The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to a carrier head for chemical mechanical polishing.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, it is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes increasingly nonplanar. This nonplanar surface presents problems in the photolithographic steps of the integrated circuit fabrication process. Therefore, there is a need to periodically planarize the substrate surface.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head. The exposed surface of the substrate is placed against a rotating polishing pad. The polishing pad may be either a xe2x80x9cstandardxe2x80x9d or a fixed-abrasive pad. A standard polishing pad has durable roughened surface, whereas a fixed-abrasive pad has abrasive particles held in a containment media. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. Some carrier heads include a flexible membrane that provides a mounting surface for the substrate, and a retaining ring to hold the substrate beneath the mounting surface. Pressurization or evacuation of a chamber behind the flexible membrane controls the load on the substrate.
A polishing slurry, including at least one chemically-reactive agent, and abrasive particles, if a standard pad is used, is supplied to the surface of the polishing pad. The chemical and mechanical interaction between the polishing pad, slurry and substrate results in polishing.
One problem, particularly in a carrier head with a flexible membrane, relates to the attachment of the flexible membrane to the carrier head. Typically, the flexible membrane is secured to the carrier head with a clamping ring. Unfortunately, there are a variety of potential problems with this arrangement, such as difficulty in securing the clamping ring or ensuring that the seal between the flexible membrane and carrier head is fluid-tight.
In general, in one aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a support structure movably connected to the base, and a flexible membrane. The support structure has an outer surface and a recess formed in the outer surface. The flexible membrane extends beneath the base to define a pressurizable chamber, and a lower surface of the flexible membrane provides a mounting surface for a substrate. An edge portion of the flexible membrane extends into the recess and a sealant in the recess secures the flexible membrane to the support structure.
Implementations of the invention may include one or more of the following. The edge portion of the flexible membrane may extend along the outer surface of the support structure. The sealant may be injected in a liquid state into the recess. A plurality of ports may be formed between an upper surface of the support structure and the recess.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a support structure movably connected to the base, and a flexible membrane. The support structure has an outer surface and a recess formed in the outer surface. The flexible membrane extends beneath the base to define a pressurizable chamber. A lower surface of the flexible membrane provides a mounting surface for a substrate. The rim portion of the flexible membrane engages the recess to form an O-ring seal between the flexible membrane and the support structure.
Implementations of the invention may include the following. The rim portion of the flexible membrane may have a diameter in an unstretched state which is less than a diameter of the recess in the outer surface of the support structure. The flexible membrane may include an edge portion that may extend along the outer surface of the support structure.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a support structure movably connected to the base, and a flexible membrane. The support structure has an outer surface and a recess formed in the outer surface. The flexible membrane extends beneath the base to define a pressurizable chamber. A lower surface of the flexible membrane provides a mounting surface for a substrate. An edge portion of the flexible membrane extends into the recess. The edge portion and recess are configured such that if the chamber is pressurized, the edge portion is pressed against a first surface of the recess to form a seal between the flexible membrane and the support structure. When the chamber is evacuated, the edge portion is pulled against a second surface of the recess to form a seal between the flexible membrane and the support structure.
Implementations of the invention may include the following. The recess may be disposed in a generally horizontal arrangement. The first surface may be a top surface of the recess and the second surface may be a bottom surface of the recess.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a support structure movably connected to the base, and a flexible membrane. The support structure has an outer surface and a recess formed in the outer surface. The flexible membrane extends beneath the base to define a pressurizable chamber. The lower surface of the flexible membrane provides a mounting surface for a substrate, and a rim portion of the flexible membrane is adhesively attached to the support structure.
Implementations of the invention may include the following. The flexible membrane may have an edge portion that extends around the outer surface of the support structure. The rim portion of the flexible membrane may be adhesively attached to a top surface of the support structure.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a flexible membrane that extends beneath the base to define a pressurizable chamber, and a retaining ring. A lower surface of the flexible membrane provides a mounting surface for a substrate. The retaining ring has an inner surface surrounding the mounting surface and a recess formed in the inner surface. An edge portion of the flexible membrane extends into the recess. The sealant in the recess secures the flexible membrane to the retaining ring.
Implementations of the invention may include the following. The sealant may be injected in a liquid state into the recess. A plurality of injection ports may be formed between an upper surface of the retaining ring and the recess. The flexible membrane may extend along the inner surface of the retaining ring.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a flexible membrane extends beneath the base to define a pressurizable chamber a lower surface of the flexible membrane provides a mounting surface for a substrate. The retaining ring surrounds the mounting surface, it includes an upper surface and a recess formed in it. The rim portion of the flexible membrane engages the recess to form an O-ring seal between the flexible membrane and the retaining ring.
Implementations of the invention may include the following. The flexible membrane may have an edge portion and may extend along the inner surface of the retaining ring.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a flexible membrane extends beneath the base to define a pressurizable chamber. The lower surface of the flexible membrane provides a mounting surface for a substrate. The retaining ring includes an inner surface surrounding the mounting surface and a recess formed in the inner surface. The edge portion of the flexible membrane extends into the recess. The edge portion and recess are configured such that if the chamber is pressurized, the edge portion is pressed against a first surface of the recess to form a seal between the flexible membrane and the retaining ring. If the chamber is evacuated, the edge portion is pulled against a second surface of the recess to form a seal between the flexible membrane and the retaining ring.
Implementations of the invention may include the following. The recess may be horizontal. The first surface may be a top surface, and the second surface may be a bottom surface of the recess.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base, a flexible membrane extends beneath the base to define a pressurizable chamber, a lower surface of the flexible membrane provides a mounting surface for a substrate. The retaining ring surrounds the mounting surface. The edge portion of the flexible membrane extends along an inner surface of the retaining ring and a rim portion of the flexible membrane is adhesively attached to a top surface of the retaining ring.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base which had an outer surface and a recess formed in the outer surface. The flexible membrane extends beneath the base to define a pressurizable chamber. A lower surface of the flexible membrane provides a mounting surface for a substrate. The rim portion of the flexible membrane engages the recess to form an O-ring seal between the flexible membrane and the base.
Implementations of the invention may include the following. The retaining ring may surround the mounting surface. The rim portion of the flexible membrane may have a diameter in an unstretched state which may be less than a diameter of the recess in the outer surface of the base.
In another aspect, the invention is directed to a carrier head for a chemical mechanical polishing apparatus including a base which has a lower surface and a recess formed in the lower surface. The flexible membrane extends beneath the base to define a pressurizable chamber. The lower surface of the flexible membrane provides a mounting surface for a substrate. The edge portion of the flexible membrane extends into the recess, it is configured so that if the chamber is pressurized, the edge portion is pressed against a first surface of the recess to form a seal between the flexible membrane and the base. If the chamber is evacuated, the edge portion is pulled against a second surface of the recess to form a seal between the flexible membrane and the base.
Implementations of the invention may include the following. The retaining ring may surround the mounting surface. The recess may be vertical. The first surface may be an outer surface, and the second surface may be an inner surface of the recess.
Advantages of the invention may include the following. The membrane is easy to install and remove, with reduced chance of assembly errors and reduced time to change the membrane. The shape of the retaining ring should not distort when the membrane is installed. The membrane assembly accommodates retaining ring wear, i.e., the pressure applied by the membrane should not change as the lower surface of the retaining ring is worn away. The membrane may be removed without removing the retaining ring. A reliable fluid-tight seal is formed between the flexible membrane and the support plate, retaining ring or base. The membrane may xe2x80x9cself-alignxe2x80x9d, i.e., pressurization of the chamber will naturally cause the membrane to move into the proper position for polishing. The membrane assembly has a low manufacturing cost. The membrane and the retaining ring or support structure may form a unitary part that is easy to install.